HEPATIC-DYSFUNCTION CAUSED BY DIETARY PRODUCTS OF LIPID-PEROXIDATION

Dietary products of lipid peroxidation cause hepatic dysfunctions such as reductions in activities of aldehyde dehydrogenase (mitochondrial NAD-dependent), succinate dehydrogenase, phosphoglucomutase, glucokinase, and glucose-6-phosphate dehydrogenase, and a depletion of coenzyme A. Toxic products in the peroxidation are considered to be the aldehydes among the decomposed products from hydroperoxides, because the decomposed products were incorporated into the liver but the other products were not when they were administered orally to rats. There are three current ideas on the causes of the dysfunctions: (a) direct attack of the incorporated aldehydes on the enzymes, (b) injury of the bio-membranes by the aldehydes, and (c) disturbance of the synthetic system for enzymes. In this study, to examine these ideas, a reasonable concentration of the peroxidation products to use in vitro was estimated from the amounts present in the liver after an oral dose of lipid peroxidation products. With respect to idea (a), when the peroxidation products were added to subcellular fractions of hepatocytes, the decomposed products specifically inactivated aldehyde dehydrogenase and glucose-6-phosphate dehydrogenase, and destroyed coenzyme A. For ideas (b) and (c), in which the parenchymal hepatocytes isolated from rat were used, the decomposed products did not seem to injure the bio-membrane, but they inhibited induction of glucokinase by hormones in the hepatocytes. It was concluded that in the hepatic dysfunction caused by the dietary products of lipid peroxidation the incorporated decomposed products in the liver directly inactivated the mitochondrial NAD-dependent aldehyde dehydrogenase and glucose-6-phosphate dehydrogenase, destroyed coenzyme A, and disturbed the synthetic system of glucokinase.